JP2020173426A - Optical element - Google Patents

Abstract

To provide an optical element equipped with an easy-to-see mark regardless of lighting conditions.SOLUTION: Disclosed is an optical element which is equipped with a mark constituted of uneven shapes. When viewed from a normal direction of the surface on which the uneven shapes are provided, the boundary between a convex part and a concave part is oriented in a plurality of directions. Accordingly, achievement of the mark with good visibility is possible regardless of the lighting conditions. Moreover, a diffraction grating configured into the mark has a plurality of unit regions, which are regions of the diffraction grating capable of emitting a specific pattern, arranged in the mark.SELECTED DRAWING: Figure 12

Description

The present invention relates to an optical element having a mark.

In recent years, the applications of sensor systems have expanded. There are various types of sensors, and the information to be detected is also different. One of the means is to irradiate an object with light from a light source and obtain information from the reflected light. For example, a pattern authentication sensor, an infrared radar, and the like are examples.

As the light source of these sensors, one having a wavelength distribution, brightness, spread, etc. according to the application is used. The wavelength of light is often in the range from visible light to infrared light. In particular, infrared rays are widely used because they are not easily affected by external light, are invisible, and can observe the inside of an object. Further, as a type of light source, an LED light source, a laser light source, or the like is often used. For example, a laser light source having a small spread of light is preferably used when detecting a distant place, and an LED light source is suitable when detecting a relatively close place or irradiating a region having a certain spread. Used for.

By the way, the size, shape, etc. of the target irradiation area do not always match the spread (profile) of the light from the light source, and it is necessary to shape the light with a diffuser plate, a lens, a shielding plate, or the like. is there. Examples of the means for shaping the light include a diffractive optical element (DOE). This is an application of the diffraction phenomenon when light passes through a place where materials with different refractive indexes are arranged with periodicity. Diffractive optics are basically designed for light of a single wavelength, but theoretically it is possible to shape the light into almost any shape. Further, in the diffractive optical element, it is possible to control the uniformity of the light distribution in the irradiation region. Such characteristics of the diffractive optical element are advantageous in terms of high efficiency by suppressing irradiation to an unnecessary region and miniaturization of the device by reducing the number of light sources.
In addition, the diffractive optical element can be applied to both a parallel light source such as a laser and a diffused light source such as an LED, and can be applied to a wide range of wavelengths from ultraviolet light to visible light and infrared light. is there.

When such a diffractive optical element is applied to a high-precision sensor, very high precision is required. In order to achieve high accuracy, traceability that enables tracking of the manufacturing history of the diffractive optical element in which a defect has occurred is important. It is also necessary to accurately position the position of the element during the manufacturing process. Furthermore, it is necessary to inspect for dust and the like adhering during the manufacturing process. In order to ensure traceability, positioning, inspection, etc., a mark may be provided on the outer edge of the element or the like. Further, such a mark may be used not only in a diffractive optical element but also in, for example, an optical element provided with a microlens array.

Conventionally, it has been known to use a pattern called a regularly arranged line-and-space pattern for the purpose of improving the visibility of such marks (Patent Document 1).
However, even with the line-and-space pattern, the mark may be difficult to see depending on the lighting conditions at the time of inspection.
Alternatively, a technique is also known in which fine irregularities are formed by processing such as shot peening or sandblasting to improve visibility (Patent Document 2).
However, there are problems such as accuracy deviation due to alignment processing, difficulty in giving anisotropy to scattered light, and cost increase due to an additional process.

JP-A-2018-189939 JP-A-2015-43400

An object of the present invention is to provide an optical element having an easy-to-see mark regardless of lighting conditions.

The present invention solves the above-mentioned problems by the following solutions. In addition, in order to facilitate understanding, the description will be given with reference numerals corresponding to the embodiments of the present invention, but the description is not limited thereto.

The first invention is an optical element (1) having a mark (20, 30, 40, 50) formed by an uneven shape, and the uneven shape is a method of a surface on which the uneven shape is provided. It is an optical element (1) in which the boundary between the convex portion and the concave portion is arranged so as to face a plurality of directions when viewed from the linear direction.

The second invention is the optical element (1) according to the first invention, wherein the concave-convex shape is a polygonal line in which the boundary between the convex portion and the concave portion is a curved line and a plurality of line segments when viewed from the normal direction. The optical element (1) is characterized by including at least one of the above.

The third invention is the optical element (1) according to the first invention or the second invention, wherein the concave-convex shape is a diffraction grating, and the primary diffracted light is at least four and the biaxial direction or more. The optical element (1) is characterized by emitting a pattern.

The fourth invention is the optical element (1) according to the third invention, wherein the uneven shape is a diffraction grating, and at least 4 of the primary diffracted light when light having a wavelength of 550 nm is input from the front. The optical element (1) is characterized in that the diffraction angle of one or more patterns is 8 degrees or more.

The fifth invention is the optical element (1) according to the third invention, wherein the uneven shape is a diffraction grating, and at least 4 of the primary diffracted light when light having a wavelength of 550 nm is input from the front. The optical element (1) is characterized in that the diffraction angle of one or more patterns is 10 degrees or more.

A sixth aspect of the present invention is the optical element (1) according to any one of the third to fifth inventions, wherein the uneven shape is a unit region which is a region of a diffraction grating capable of emitting the pattern. The optical element (1) has (1001, 1002), and the unit regions are arranged in a plurality of the marks (20, 30, 40, 50).

The seventh invention includes an optical functional region (10) that exhibits the optical function of the optical element (1) in the optical element (1) according to any one of the first to sixth inventions. , The mark (20, 30, 40, 50) is an optical element (1) characterized in that it is arranged around the optical functional region (10).

The eighth invention is the optical element (1) according to the seventh invention, wherein the optical functional region (10) includes a diffraction grating.

The ninth invention is characterized in that, in the optical element (1) according to the eighth invention, the uneven shape is a diffraction grating and has the same uneven height as the diffraction grating in the optical functional region. It is an optical element (1).

The tenth invention is the optical element (1) according to the eighth invention or the ninth invention, wherein the concave-convex shape is a diffraction grating and has the same design as the diffraction grating of the optical functional region (10). The optical element (1) is characterized by being composed of a diffraction grating.

According to the present invention, it is possible to provide an optical element having a mark that is easy to see regardless of the lighting conditions.

It is a figure which shows the embodiment of the diffraction optical element 1 by this invention. It is sectional drawing which cut at the position of the arrow GG in FIG. It is a top view which shows the example of the diffraction optical element which the uneven shape of the diffraction grating seen from the normal direction of a sheet surface is formed into the regular or irregular pattern which the boundary between the convex part and the concave part includes a curve. Top view showing an example of a diffraction optical element in which the concave-convex shape of a diffraction grating viewed from the normal direction of the sheet surface is formed in a grid-like pattern in which a plurality of unit cells in which the same uneven shape is arranged side by side are tiling. Is. It is a perspective view which shows an example of the partial periodic structure in the example of the irregular type diffraction optical element shown in FIG. It is a perspective view which shows an example of the partial periodic structure in the example of the GCA type diffractive optical element shown in FIG. It is sectional drawing which cut | cut the diffractive optical element at the position of the arrow GG'in FIG. It is a figure explaining the diffraction optical element. It is a figure which shows the multi-imposition body 500 which the diffractive optical element 1 is multi-imposed. It is an enlarged view of a part of a multi-imposition body 500. It is a figure explaining the foreign matter inspection. It is an enlarged view which showed the region where the mold identification code 20 was formed. It is an enlarged view which showed the region where the defect mark 40 was formed. It is a figure explaining the concave-convex shape formed in the mold identification code 20 and the like. It is a figure which shows another example of a diffraction grating which is desirable to be constructed in a unit area. It is a figure which shows the result of having evaluated the visibility about the comparative example and this embodiment. It is a figure which shows the result of having compared the diffractive optical element provided with the defect mark of this embodiment with the comparative example provided with the conventional defect mark.

Hereinafter, the best mode for carrying out the present invention will be described with reference to drawings and the like.

(Embodiment)
FIG. 1 is a diagram showing an embodiment of the diffraction optical element 1 according to the present invention.
FIG. 2 is a cross-sectional view cut at the position of arrows GG in FIG.
In addition, each figure shown below including FIG. 1 and FIG. 2 is a diagram schematically shown, and the size and shape of each part are exaggerated as appropriate for easy understanding.
Further, in the following description, specific numerical values, shapes, materials and the like will be described, but these can be changed as appropriate.
In addition, the terms used in the present invention that specify the shape and geometric conditions and their degrees, such as terms such as "parallel", "orthogonal", and "same", and length and angle values, are used. Without being bound by the strict meaning, we will interpret it including the range where similar functions can be expected.
Further, in the present invention, the term "transparent" means a substance that transmits light of at least the wavelength to be used. For example, even if it does not transmit visible light, if it transmits infrared rays, it shall be treated as transparent when used for infrared applications.

The diffraction optical element 1 of the present embodiment includes a base material 1a and a resin layer 1b.
The base material 1a is a layer that is a base of the diffraction optical element 1, and various transparent resin films, resin sheets, and the like can be used.
Examples of the base material 1a include polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, methyl methacrylate butadiene styrene (MBS) resin, methyl methacrylate styrene (MS) resin, and acrylic styrene (AS) resin. , Acrylonitrile-butadiene-styrene (ABS) resin and other transparent resins can be used. Further, the base material 1a may be formed by using a glass base material. Although not shown, an adhesion layer may be provided on the base material 1a to improve the adhesion with the applied ultraviolet curable resin or the like.

The resin layer 1b is formed on the base material 1a and has a shaped shape (10, 20, 30, 40, 50, etc.) corresponding to the shape formed in the molding mold. The resin layer 1b uses a molding mold in which a concavo-convex pattern corresponding to each of the above-mentioned shaped shapes is formed, and for example, an ultraviolet curable resin applied on the base material 1a is molded to transfer the concavo-convex pattern. , Can be formed by irradiating with ultraviolet rays and curing.

As the ultraviolet curable resin, for example, urethane acrylate-based, polyester acrylate-based, epoxy acrylate-based, polyether acrylate-based, polythiol-based, butadiene acrylate and the like can be used. The material for forming the resin layer 1b is not limited to the ultraviolet curable resin. The resin layer 1b may be formed of, for example, an electron beam curable resin. Further, the resin layer 1b may be formed by using a thermosetting type or an ultraviolet curable type SOG (Spin on Glass). Further, each of the above patterns is not limited to the example of being transferred from the original plate by shaping, and may be shaped by using an intermediate plate of a resin produced from the original plate having the uneven shape of each of the above patterns.

The resin layer 1b includes a diffraction grating 10, a mold identification code 20, a position identification code 30, a defect mark 40, and a cutting position mark 50 as shaped shapes.

The diffraction grating 10 is arranged in the center of the diffraction optical element 1 and is composed of a large number of fine uneven shapes. The diffraction grating 10 is an optical functional region that exerts an optical function originally intended for the diffraction optical element 1, and is different from the diffraction grating provided in the defect mark described later.
FIG. 3 is a plane showing an example of a diffraction optical element in which the uneven shape of the diffraction grating viewed from the normal direction of the sheet surface is formed in a regular or irregular pattern in which the boundary between the convex portion and the concave portion includes a curved line. It is a figure.
In the present embodiment, as an example, it can be applied to a diffractive optical element having a seemingly irregular uneven shape pattern as shown in FIG. In the following description, the type of diffractive optical element shown in FIG. 3 will also be referred to as an irregular type. However, since this irregular pattern may be a regular pattern depending on the target emission pattern of the diffractive optical element, the term "irregular type" is a name for convenience and is limited to irregularity. It's not something to do. Further, in FIG. 3, the irregular pattern is composed of curved lines, but depending on the target emission pattern of the diffractive optical element, it is a straight line or a polygonal line connecting line segments composed of curved lines. May include. Therefore, in the irregular diffraction grating pattern, the boundary between the convex portion and the concave portion is connected to the curve and a plurality of line segments when viewed from the normal direction of the surface on which the uneven shape of the high refractive index portion (described later) is formed. Includes at least one with the polygonal line. Further, a specific irregular pattern may be used as a unit cell, and a large number of the unit cells may be arranged in a grid pattern.

FIG. 4 shows an example of a diffraction optical element in which the uneven shape of the diffraction grating viewed from the normal direction of the sheet surface is formed in a grid-like pattern in which a plurality of unit cells in which the same uneven shape is arranged side by side are tiling. It is a top view which shows.
In the present embodiment, as another example, as shown in FIG. 4, it can be applied to a diffraction optical element in which unit cells in which the same uneven shape is arranged side by side are formed in a grid pattern in which a plurality of tilings are formed. it can. In the following description, the type of diffractive optical element shown in FIG. 4 will also be referred to as a grating cell array type or a GCA type. In the grating cell array type diffractive optical element, the direction and angle of the light diffracted by the diffraction grating are different for each unit cell, and by tying a large number of unit cells, the desired optical characteristics can be obtained. The element is configured. That is, in the grating cell array type diffractive optical element, the high refractive index portion is partitioned in a lattice pattern when viewed from the normal direction of the surface on which the uneven shape is formed, and extends in a specific direction within the partition. The convex portions having the same shape are arranged side by side in a direction orthogonal to the specific extending direction, and the width and extending direction of the convex portions are different for each section.

FIG. 5 is a perspective view showing an example of a partial periodic structure in the example of the irregular diffractive optical element shown in FIG.
FIG. 6 is a perspective view showing an example of a partial periodic structure in the example of the GCA type diffractive optical element shown in FIG.
FIG. 7 is a cross-sectional view of the diffractive optical element cut at the position of the arrow GG'in FIG.
FIG. 8 is a diagram illustrating a diffractive optical element.

In the present invention, "shaping the light" means controlling the traveling direction of the light so that the shape of the light projected on the object or the target area (irradiation area) becomes an arbitrary shape. .. For example, as shown in the example of FIG. 8, a light source unit 210 that emits light 201 (FIG. 8 (b)) whose irradiation region 202 becomes circular when directly projected onto a flat screen 200 is prepared. By transmitting the light 201 through the diffractive optical element 1 of the present invention, the irradiation region 204 can be made into a desired shape such as a square (FIG. 8 (a)), a rectangle, or a circle (not shown). It is called "shaping the light".
By combining the light source unit 210 and the diffractive optical element 1 of the present embodiment, which is arranged at least one at a position where the light emitted by the light source unit 210 passes, light that can be irradiated in a shaped state. It can be an irradiation device.

The diffractive optical element 1 of the present embodiment is a diffractive optical element (DOE) that shapes light. The diffraction grating 10 of the diffractive optical element 1 has a cross-shaped shape, specifically, for example, ± 50 degrees and a width of ± 3.3 with respect to the light from the light source unit 210 that emits light having a wavelength of 500 nm. It is designed to spread the light in a shape in which two bands of light that spread with degree have two tolerances.
The diffraction grating 10 of the present embodiment has a different depth at each position of A, B, C, and D shown in FIG. That is, the diffraction grating 10 is composed of a multi-step shape having four steps of different heights. The diffraction grating 10 usually has a plurality of regions having different periodic structures (partial periodic structure: for example, E and F regions in FIG. 3). In FIGS. 5 and 6, an example of the partial periodic structure is extracted and shown.

As shown in FIG. 7, the diffraction grating 10 includes a high refractive index portion 11 in which a plurality of convex portions 11a are arranged side by side in a cross-sectional shape. In the GCA type diffractive optical element, the high refractive index portion 11 extends in the depth direction of the cross section while maintaining the same cross-sectional shape. On the other hand, in the irregular diffractive optical element, the cross-sectional shape changes when the cross-sectional position changes, and a large number of diffraction gratings having various cross-sectional shapes are arranged.

Further, air is present in the upper portion of FIG. 3 including the concave portion 12 formed between the convex portions 11a and the space 13 near the top of the convex portion 11a, and the refractive index is higher than that of the high refractive index portion 11. Is a low refractive index portion 14. A diffraction layer 15 having an action of shaping light is formed by a periodic structure in which these high refractive index portions 11 and low refractive index portions 14 are arranged alternately.

The convex portion 11a has a multi-step shape having four stepped portions having different heights on one side of the side surface shape (left side in FIG. 7). Specifically, the convex portion 11a is from the most protruding level 3 step portion 11a-3, the level 2 step portion 11a-2 which is one step lower than the level 3 step portion 11a-3, and the level 2 step portion 11a-2. Also has a level 1 step portion 11a-1 which is one step lower and a level 0 step portion 11a-0 which is one step lower than the level 1 step portion 11a-1 on one side surface side. Further, the other side (right side in FIG. 7) of the side surface shape of the convex portion 11a is a side wall portion 11b that connects the level 3 step portion 11a-3 to the level 0 step portion 11a-0 in a straight line.
The convex portion 11a of the present embodiment is a shape that imitates the sawtooth shape by a multi-step contour shape, and since the four-level form has been described, the convex portion 11a is a relatively coarsely imitated form. If the number of levels is further increased, the shape can be more accurately imitated.

FIG. 9 is a diagram showing a multi-imposition body 500 on which the diffraction optical element 1 is multi-imposed.
FIG. 10 is an enlarged view of a part of the multi-imposition body 500.
Since the diffractive optical element 1 of the present embodiment is, for example, a very small member having an outer shape of about 3 mm × 3 mm, a large number of diffractive optical elements 1 are latticed as shown in FIG. 9 during the manufacturing process. It is manufactured as a multi-imposition body 500 arranged side by side in a shape to improve the efficiency of the manufacturing process. The diffraction optical element 1 is manufactured by cutting the multi-imposition body 500 into individual pieces. In FIG. 9, a boundary line is drawn with a solid line at the boundary between adjacent diffractive optical elements 1 for easy understanding, but since this boundary line is not formed before cutting, FIG. Then, it is shown by a two-dot chain line. In addition, in FIG. 9, in order to enable illustration and to facilitate understanding, a total of 100 diffractive optical elements 1 in 10 rows × 10 columns are arranged in the illustration. However, in reality, more diffractive optical elements 1 are arranged. For example, there are cases where thousands to tens of thousands of diffractive optical elements 1 are arranged on one multi-imposition body 500.
In the following description, the description will be made on the premise that the diffraction optical element 1 is cut from the multi-imposition body 500 in this way.

Returning to FIGS. 1 and 2, the mold identification code 20 is a mark for identifying the mold, and is described as “900A” in the example shown in FIG. The mold identification code 20 is a code unique to the mold, and the mold identification code 20 can be used to determine which molding mold the diffractive optical element 1 is molded from. Since the mold identification code 20 is a code unique to the mold, it has the same code in all the diffraction optical elements 1 in the multi-imposition body 500 (see FIG. 10).

The position identification code 30 is a mark for identifying the position of the diffraction optical element 1 in the molding die. In the example of FIG. 9, since there are 100 parts for molding the diffractive optical element 1 in one molding mold, it is possible to specify at which position among these 100 parts the diffractive optical element 1 is molded. A position identification code 30 is provided as a code. In the example of FIG. 1, an example of "X49, Y53" is shown, which is the 49th column in the X direction (horizontal direction in FIGS. 9 and 10) and in the Y direction (FIG. 9, 10). It indicates that it is the position of the 53rd row in the vertical direction at 10. It should be noted that the display is not limited to the column number and the row number as in this example, and may be numerical values in order from 1. Further, the mold identification code 20 and the position identification code 30 may be combined to form a single code having both functions. For example, "900A-X49Y53" may be used as an example in the above case.

In the present embodiment, the first code region is arranged in the rectangular region on the left half and the second code region is arranged in the rectangular region on the right half when the diffraction optical element 1 is viewed from the normal direction of the surface on which the concave-convex shape is provided. The first code region and the second code region are configured to include one of the mold identification code 20 and the position identification code 30, respectively. Specifically, when the molding type identification code 20 is included in the first code area, the position identification code 30 is included in the second code area, and vice versa. That is, the mold identification code 20 and the position identification code 30 are arranged at a sufficient distance from each other, so that they can be recognized as different codes.
Further, a specific identification code may be provided for each so that the molding type identification code 20 and the position identification code 30 can be distinguished from each other. For example, a unique symbol may be added to each acronym of the molding type identification code 20 and the position identification code 30. Specifically, for example, "M (Master)" is used for the mold identification code 20, "X (X-Coordinate)" is used for the X coordinate of the position identification code 30, and "Y (Y-Coordinate)" is used for the Y coordinate. ) ”Is given.
By providing the molding die identification code 20 and the position identification code 30, it is possible to easily identify which molding die and which position the product was manufactured in, even if the diffractive optical element 1 is individualized. It is possible.

The defect mark 40 is a mark formed to a predetermined size and is provided for reference by an inspector during a visual inspection. Alternatively, it may be used as a criterion for automatic inspection by an inspection device. For example, even if an inspection standard is set that a defect larger than 40 μm is regarded as a defective product, it is difficult to determine the size only by training an inspector. It is also difficult to unify the judgment criteria for each inspector. Therefore, by making it possible to observe the part where there is a possibility of a defect in comparison with the defect mark 40, it is possible to improve the accuracy of inspection pass / fail judgment and the improvement of inspection tact, and to facilitate the development of inspector skills. ..

When one defect mark 40 is provided, it is desirable that the dimension be a threshold value for determining a defect or a dimension slightly smaller than the threshold value. For example, when a defect larger than 40 μm is regarded as a defective product as described above, the defect mark 40 is a square of 40 μm × 40 μm, a circle of 40 μm in diameter, or a square of 30 μm × 30 μm. Alternatively, it may be a circle with a diameter of 30 μm. Further, the shape is not limited to a square or a circle, but may be a rectangle, an ellipse, or the like. Further, if the tendency of the defect to be generated is known, the defect mark 40 may be formed in a shape close to the defect to facilitate comparison at the time of inspection. For example, when the adhesion of hair occurs frequently as a defect, the defect mark 40 may be formed in a rectangle of, for example, 10 μm × 2000 μm.

Further, in the present embodiment, three defect marks 40a, 40b, and 40c having different dimensions are arranged side by side in order of size. In the present embodiment, as described above, when a defect larger than 40 μm is assumed to be a defective product, the defect mark 40a is a square of 40 μm × 40 μm, and the defect mark 40b is 30 μm × 30 μm. It is a square, and the defect mark 40a is a square of 20 μm × 20 μm. By arranging the defect marks 40 whose dimensions gradually change at a constant rate in this way, when the inspector observes the object (part where there is a possibility of defect), the size can be quickly and accurately determined. You can expect the effect of grasping well. In addition, numbers or the like indicating the sizes of the defect marks 40a, 40b, and 40c may be further arranged near each defect mark.

The cutting position mark 50 is a mark used as a guide for the cutting position when the multi-imposition body 500 is cut into individual pieces of the diffractive optical element 1. The cutting position mark 50 may remain on the diffractive optical element 1 after cutting as shown in FIG. 1, or may be configured so as to be removed at the time of cutting and not remain on the diffractive optical element 1.

FIG. 11 is a diagram illustrating a foreign matter inspection.
In the diffractive optical element 1 of the present embodiment, when the foreign matter P is observed during the foreign matter inspection, for example, as shown in FIG. 11, the defect mark 40 and the foreign matter P can be compared and observed in the same field of view of the microscope. Therefore, it is possible to perform a visual inspection with high accuracy, quickly and easily. When this inspection is performed by a plurality of inspectors, it is possible to suppress variations in inspection accuracy by the inspectors and realize stable and high-precision inspections by providing the defect mark 40.
Alternatively, when performing automatic inspection by image analysis, the defect mark 40 can be used as a calibration value in image analysis, and high-precision inspection can be realized by suppressing variations in inspection sensitivity of the multi-imposition body.

Here, when inspecting a foreign substance or the like as shown in FIG. 11, in many cases, the lighting state at the time of microscopic observation is switched in order to make it easier to see defects such as the foreign substance. That is, observation is performed by causing all of the lighting devices provided with the plurality of light emitting units to emit light or only a part of the lighting device to emit light. In addition, the angle and position of the lighting device may be adjusted. Conventionally, when a mark is given to an optical element, the mark is simply formed into a convex or concave shape, or a regularly arranged pattern called a line-and-space pattern is formed on the mark.
However, depending on the lighting conditions, the conventional mark may have poor visibility. Therefore, in the present embodiment, a special pattern for improving visibility is configured for all the marks of the mold identification code 20, the position identification code 30, the defect mark 40, and the cutting position mark 50. In the following description, the mold identification code 20, the position identification code 30, the defect mark 40, and the cutting position mark 50 are collectively referred to as a mark.

FIG. 12 is an enlarged view showing a region in which the mold identification code 20 is formed.
FIG. 13 is an enlarged view showing a region where the defect mark 40 is formed.
The molding type identification code 20 and the defect mark 40 of the present embodiment are formed with an uneven shape constituting a diffraction grating. Further, although not shown, the position identification code 30 and the cutting position mark 50 also have a concave-convex shape forming a similar diffraction grating.

FIG. 14 is a diagram for explaining the uneven shape formed on the mold identification code 20 and the like.
The uneven shape provided on the mark of the present embodiment has a region in which a diffraction grating having a size of 3 μm × 3 μm shown in FIG. 14 (a) is arranged as one unit (hereinafter, referred to as a unit region 1001). A plurality of the unit regions 1001 are closely arranged and arranged in the mark. The diffraction grating formed in the unit region 1001 in the present embodiment is a two-level diffraction grating, and the uneven shape thereof includes a convex portion and a concave portion when viewed from the normal direction of the surface on which the diffraction grating is formed. The boundary includes both a curve and a polygonal line connecting multiple line segments. In FIG. 14A, the portion shown in black has a convex shape.
Here, for example, the unit area may be cut out from a size larger than the mark to the size of the mark, such as 500 μm, and even in this form, light can be emitted in a wide range. However, in the case of this form, although most of the light is emitted at the same position as the irradiation spot intended at the time of design, the intensity balance may greatly deviate from the intensity balance intended at the time of design, for example, one side of a rectangular mark. The edge of the mark has high visibility, but the edge on the opposite side has low visibility, and the light emitted from the mark may be biased. Therefore, it is desirable that the size of the unit area is smaller than the mark.

The unit region 1001 of the present embodiment constitutes a pattern in which 5 × 5 irradiation spots SP as shown in FIG. 14B are arranged at equal intervals in the wave number space when light of the corresponding wavelength is irradiated. It emits light. Since the unit regions 1001 are closely arranged on the mark, when the mark is irradiated with light having a corresponding wavelength, 5 × 5 irradiation spots SP as shown in FIG. 14B have wave numbers. Light that constitutes a pattern arranged at equal intervals in space is emitted.
For the design of the diffraction grating pattern (FIG. 14 (a)) for diffracting light into such a desired irradiation pattern (FIG. 14 (b)), for example, IFTA (Iterative Fourier Transform Algorithm) can be used. This IFTA is a design method that repeats the Fourier transform while moving a figure, and is generally used. By using this IFTA, it is possible to design a diffraction grating at high speed and with extremely high accuracy for a target (design aim).
The pattern emitted from the unit region 1001 is not limited to the form shown in FIG. 14B, and may be another pattern. However, it is desirable that the pattern emitted from the unit region 1001 is a diffraction grating emitted in a wide range in order to improve visibility from various directions.

FIG. 15 is a diagram showing another example of a diffraction grating that is preferably configured in a unit region.
As shown in FIG. 15A, the region in which the diffraction gratings having a size of 8 μm × 8 μm are arranged is defined as the unit region 1002. This diffraction grating is also a two-level diffraction grating, and its uneven shape is such that the boundary between the convex portion and the concave portion when viewed from the normal direction of the surface on which the diffraction grating is formed connects a curved line and a plurality of line segments. Includes both with a polygonal line. When the unit region 1002 is irradiated with light of the corresponding wavelength, 11 × 11 irradiation spots SP as shown in FIG. 15B form a pattern in which 11 × 11 irradiation spots SP are arranged at equal intervals in the wave number space. Emit light.

In each of the diffraction gratings of FIGS. 14 (a) and 15 (a), the concave-convex shape is a polygonal line in which the boundary between the convex portion and the concave portion is a curved line and a plurality of line segments when viewed from the normal direction. Both are included. The concave-convex shape is arranged so that the boundary between the convex portion and the concave portion faces in a plurality of directions when viewed from the normal direction of the surface on which the concave-convex shape is provided. As a result, light emitted from various directions can be emitted in various directions, and even when the direction of illumination is changed to see light-scattering transparent foreign matter, opaque foreign matter, scratches, etc., the mark is displayed. By adopting a structure that bends light, it is possible to make a clear difference in the scattering and transmission behavior of the base base material and the mark with respect to the light source from various directions, and the mark with excellent visibility can be obtained.

Here, the light of the corresponding wavelength may be appropriately selected to design the diffraction grating of the unit region 1001 (or the unit region 1002), but the wavelength close to the wavelength of the light used at the time of observation improves the visibility. Desirable for. In the present embodiment, since the observation is performed with visible light, a diffraction grating that emits the above pattern with light having a wavelength of 550 nm is configured in the unit region 1001.
The illumination device for observation is often a so-called dark field illumination, which illuminates from an angle. Assuming that this illumination light is bent by a marker and put into the objective lens, it is desirable that any of the irradiation spots SP shown in the present embodiment has a diffraction angle of 8 degrees or more, more preferably 10 degrees or more. ..

FIG. 16 is a diagram showing the results of evaluating the visibility of the comparative example and the present embodiment.
In the method using dark-field illumination, by irradiating light from an angle or the like so that the light does not directly enter the objective lens, only the light scattered or diffracted by the mark can be observed. Mark visibility is improved compared to the method used. This can be seen from the fact that the result of Comparative Example 2 is improved as compared with the case of Comparative Example 1 in which the bright field is adopted.

The diffraction grating can be arbitrarily set by its design. Therefore, using a line-and-space pattern with a simple shape (indicated as L / S in FIG. 16), mark base materials having different line widths are prepared in order to confirm the mark visibility, and the inspection visibility is evaluated. Carried out. The line-and-space pattern also has a function of diffracting light as a diffraction grating. Two types of line widths, 4 μm and 2 μm, were evaluated.
As a result, it was confirmed that the mark visibility was improved in Comparative Example 3 having a width of 2 μm as compared with Comparative Example 2 having a width of 4 μm.
Further, when the diffraction angle is calculated by the theoretical formula of the diffraction angle sin θ = λ / pitch, the diffraction angle of Comparative Example 2 having a line width of 4 μm is 4 degrees, whereas that of Comparative Example 3 having a line width of 2 μm is 8 degrees. It can be seen that the larger the size, the better the visibility.
Based on the above, the diffraction angle of the primary light is preferably 8 degrees or more, more preferably 10 degrees or more.

However, it was confirmed that in the line-and-space pattern, the visibility of the mark deteriorates when the base material set position (mark line arrangement direction) is rotated 90 degrees with respect to the irradiation direction of the dark field illumination (Comparative Example 4).
In order to improve this problem, a mark base material having two or more DOE patterns developed on two axes whose primary diffraction angles are orthogonal to each other was prepared, and an inspection visibility evaluation was performed. As a result, the base material set position ( The mark visibility did not change even when the mark line arrangement direction was rotated from 0 degrees to 90 degrees, and the visibility was further improved (this embodiment).
From the above, it can be said that it is desirable that the primary diffracted light emits at least four or more patterns and two or more axial directions.

Further, as a method of forming a diffraction grating on the mark, in the present embodiment, the diffraction grating 10 can be produced at the same time as the production of the diffraction grating 10 by using the step of producing the diffraction grating 10, and the production can be easily performed. Therefore, the manufacturing cost of the diffractive optical element 1 does not increase by providing the mark of the present embodiment.

In verifying the scattering and transmission characteristics of a mark composed of a diffraction grating, a spot beam smaller than the mark or similar to the mark is applied, and the scattered light and transmitted light are projected onto a screen for observation. A means of directly observing the scattered light and the transmitted light with a detector such as CMOS or CCD can be mentioned.
Alternatively, the shape of the mark can be identified and the scattering and transmission characteristics can be verified by simulation. Specifically, by acquiring the pattern from the upper part with a microscope or SEM and extracting the contour, it can be used as the input value of the plan view of the simulation, and the height of the unevenness can be acquired with AFM or SEM. If possible, it can be an input value in the height direction of the simulation. This simulation may be either a Thin model by Fourier transform or the like and a Rigorous model by RCWA or FDTD or the like. When the Thin model is used, the height of the unevenness can be converted into a phase difference and input to obtain an input value in the height direction. When the Rigorous model is used, the unevenness height can be used as an input value of the simulation height as it is, and the unevenness height by AFM or SEM may be an average value of the measurement results.

As the form of the light source, a wavelength of 550 nm, which is a typical value of visible light, can be used, and characteristics due to orthogonal linearly polarized light such as deviation angles of 0 degrees and 90 degrees may be calculated and used as the average value. Here, when calculating the phase difference or using the simulation height, the refractive index of the base material and the optical element portion is required, and this refractive index is a representative assumed from the composition of the material of the optical element. You may enter a value, for example, for borosilicate glass, the refractive index will be in the range of 1.45 to 1.5 for a wavelength of 550 nm, and for general photocurable resins, 1.45 to 1. Often the index of refraction is in the range of 6.6. On the other hand, when the individual piece size of the optical element is large, the refractive index can be acquired by a measuring device such as an ellipsometer, and the value may be input.

FIG. 17 is a diagram showing the result of comparing the diffractive optical element provided with the defect mark of the present embodiment with the conventional comparative example having the defect mark.
As the sample prepared in the comparison shown in FIG. 17, the conventional form in which the line and space is formed on the defect mark is referred to as Comparative Example 1 to Comparative Example 3, and the sample of the present embodiment is provided on the defect mark by forming a diffraction grating. From 1 to Example 3. In FIG. 17, the position corresponding to the defect mark 40 is enlarged and shown. Further, the defect marks in FIG. 17 have a configuration in which four are provided.

In Comparative Examples 1 to 3, the mark configurations are the same line and space, but the lighting conditions are different. Comparative Example 1 is an illumination state (hereinafter, bright field) in which all the lights arranged around the objective lens of the microscope are turned on. Comparative Example 2 is an illumination state (hereinafter, dark field) in which the lights arranged around the objective lens are partially turned off. Comparative Example 3 is a finely adjusted illumination state (hereinafter referred to as a special dark field) in which a part of the lights arranged around the objective lens is turned off.
Similarly, in Examples 1 to 3, the mark configuration is the same diffraction grating, but the illumination conditions are different. Example 1 is a bright field, Example 2 is a dark field, and Example 3 is a special dark field.

As shown in FIGS. 17 (a) to 17 (c), in Comparative Examples 1 to 3, the defect mark may be difficult to see due to changes in lighting conditions. On the other hand, as shown in FIGS. 17 (d) to 17 (f), in the first to third embodiments, the entire surface and the outline of the defect mark can be clearly seen even if the lighting conditions are changed. Since it is shown as a black-and-white photograph in FIG. 17, it may be difficult to understand the difference between the comparative example and the example, but in the actual observation field of view, the difference more remarkable than that shown in FIG. It appeared between the example.

As described above, the diffraction optical element 1 of the present embodiment has a diffraction grating formed on all the marks of the molding type identification code 20, the position identification code 30, the defect mark 40, and the cutting position mark 50. .. Therefore, the mark with good visibility can be obtained regardless of the lighting conditions.
(Transformed form)
Not limited to the embodiments described above, various modifications and changes are possible, and these are also within the scope of the present invention.

(1) In the embodiment, the uneven shape of the diffraction grating formed as a mark is such that the boundary between the convex portion and the concave portion is a curved line and a plurality of line segments when viewed from the normal direction of the surface on which the diffraction grating is formed. An example of a complicated configuration including both a connected polygonal line and an example was explained. Not limited to this, for example, the diffraction grating formed on the mark may be a grating cell array as shown in FIG. However, when the grating cell array is formed as a mark, it is desirable that a plurality of types of diffraction gratings are arranged even in a portion where the width of the mark is narrow.

(2) In the embodiment, the diffraction grating provided on the mark will be described with reference to an example in which the diffraction grating 10 is different from the diffraction grating 10 which is an optical functional region exhibiting the original intended optical function of the diffraction optical element 1. did. Not limited to this, for example, the diffraction grating provided on the mark may be a diffraction grating having the same configuration as the diffraction grating 10 which is an optical functional region that exerts the originally intended optical function of the diffraction optical element 1. As a result, the manufacturing process can be simplified. Further, the diffraction grating provided on the mark and the diffraction grating 10 which is an optical functional region that exerts an optical function may have different or the same height of unevenness. When the heights are the same, the manufacturing process can be simplified, for example, when the mold is manufactured in the lithography process.

The height of the unevenness described here is defined by a partial extraction of an observation area of several tens of μm that can be observed by AFM, SEM, etc., and the average height difference between the convex and concave parts of the pattern shape or the convex and convex parts. It is desirable to do. Specifically, in the case of the multi-stage structure as shown in FIG. 7, there are a plurality of convex portions, but not only between 11a-3 and 11a-0, but also between 11a-3 and 11a-2, or 11a-3. Any step may be used to define the average height difference, such as 11a-1. This is because, in the manufacturing process of a multi-stage mold, marks can be created at the same time regardless of which stage is created.
Furthermore, when comparing the average height difference between the diffraction grating provided on the mark and the diffraction grating which is an optical functional region that exerts an optical function, even if there is a difference of about 30%, it can be regarded as the same height. .. This is because, as shown in FIG. 14, the pattern width of the diffractive optical element is often submicron or smaller, and in the processing of such a fine pattern, the etching depth of the lithography process depends on the pattern width. This is because large manufacturing errors often occur, such as changes in.

(3) In the embodiment, the diffraction optical element 1 in which the optical functional region exhibiting the optical function originally intended of the optical element is the diffraction grating 10 has been described as an example. Not limited to this, for example, the optical functional region that exerts the optical function originally intended of the optical element may be, for example, a microlens array or the like, and is not limited to the diffractive optical element but may be an optical element having another configuration. The invention may be applied.

(4) In the embodiment, the diffraction grating formed by the mark has been described with an example of having a two-level uneven shape. Not limited to this, for example, the diffraction grating formed in the mark may be 4 levels, 8 levels, or the like, and the number of steps of the uneven shape of the diffraction grating can be appropriately changed.

(5) In the embodiment, the diffraction optical element 1 has been described with reference to an example in which the molding type identification code 20, the position identification code 30, the defect mark 40, and the cutting position mark 50 are provided. Not limited to this, for example, each diffractive optical element 1 may be provided with a unique variable code (hereinafter, referred to as a base material ID) capable of individually specifying the multiimposition body 500 that shapes the shaped shape. Good. For the base material ID, for example, a unique reference numeral can be provided for each base material 1a prepared for producing the multi-imposition body 500. This code may be a simple serial number, a code related to the shaping processing date and time of the multiimposition body 500, or various codes such as a bar code and a two-dimensional code associated with them. There may be.

(Position where base material ID is provided)
It is necessary that the base material ID does not affect the optical characteristics of the element, and it is usually preferable to give the base material ID outside the effective area where the element is exposed to light, but a method that does not affect the light used is used. This is not the case when taking. For example, when a substantially transparent ink is used at a target wavelength, the base material ID may be provided in an effective area where the element is exposed to light.
Further, it may be on the optical element surface (fine uneven side) or on the back surface thereof, but when it is applied before the molding, it is formed on the surface opposite to the molding surface in consideration of the influence on the molding process. It is preferable to do so. When it is applied after molding, it may be applied to the resin surface or the back surface, and when it is applied after being individualized, it may be applied to the side surface of the element. The method of applying to the side surface is effective when the effective area of the element is wide and the place to apply is too narrow, and the element is applied in a picked-up state.

(Timing of setting the base material ID)
It is conceivable that the process is applied to the molding base material before shaping, added after molding, given after inspection, and given to each chip after dicing. Since the base material ID given to the chip is difficult to see when the chip size is small, the base material ID having a size that can be visually recognized as the shaping base material is considered when the process is carried out in the base material state. May be used in combination with the operation of granting.

(Method of providing base material ID)
As a method for assigning a base material ID, a method such as laser marking, an inkjet, or a stamp can be applied. Even if it cannot always be visually identified, it is sufficient that the drawing pattern can be identified by comparing it with the base portion with a microscope, a depth sensing device, or the like.
There are various methods for laser marking, but the method is appropriately selected according to the material of the surface to be applied and the drawing size. A method involving evaporation of a material tends to lead to the generation of foreign matter, and an excimer laser is preferable for a resin material. When engraving on a glass substrate, there is a concern that it will be easily damaged, so the depth should be as shallow as possible (several μm or less). In addition, a method of developing a color of a resin material such as foaming or carbonization can also be applied. In that case, the contrast with the non-drawing portion may be added, and a method of changing the shape of the background uneven pattern formed in advance by laser irradiation and adding contrast by changing the shape may be used. The uneven pattern is not particularly limited, but if it has the same shape as the defect mark, it will be easier to see later.
Further, as a method of assigning the base material ID, a method of adhering ink by an inkjet, a stamp, or the like can also be used. When using a stamp, use one whose number can be changed for each base material. The ink to be used may be appropriately selected from those normally used for industrial purposes according to the material of the printing surface, wettability, etc., but the ink that does not disappear in the environmental test is selected. Further, when the target wavelength at the time of use is substantially transparent, the restriction on the printing place is relaxed. For example, in the case of an optical element for infrared rays, it is possible to print in the effective area by using an ink that transmits infrared rays. In that case, the display size of the base material ID can be made relatively large, and detection becomes easy. In addition, since it is necessary to avoid the effective area of the element in methods such as laser, inkjet, and stamping, accurate drawing position control is required, but when using substantially transparent ink, the alignment accuracy is relaxed and the process Likelihood increases.

By providing the base material ID in each diffractive optical element, the lot of the shaped base material itself can be identified from the individualized diffractive optical element itself. The information associated with the base material ID is information necessary for ensuring traceability, such as "lot of base material used", "lot of material used", and "date of shaping". Since the base material ID is provided on each diffractive optical element together with the mold identification code and the position identification code, the diffractive optical element itself mounted on the assembled product, the lot of DOE, and the original plate can be traced. It is possible to do.

The embodiment and the modified form may be used in combination as appropriate, but detailed description thereof will be omitted. Moreover, the present invention is not limited to each of the embodiments described above.

1 Diffractive optical element 1a Base material 1b Resin layer 10 Diffractive grating 11 High refractive index part 11a Convex part 11b Side wall part 12 Recessed part 13 Space 14 Low refractive index part 15 Diffractive layer 20 Molding type identification code 30 Position identification code 40, 40a, 40b , 40c Defect mark 50 Cutting position mark 200 Screen 201 Light 202 Irradiation area 204 Irradiation area 210 Light source 500 Multi-imposition body 1001,1002 Unit area

Claims (10)

An optical element having a mark composed of an uneven shape.
The uneven shape is an optical element in which the boundary between the convex portion and the concave portion is arranged so as to face in a plurality of directions when viewed from the normal direction of the surface on which the uneven shape is provided. In the optical element according to claim 1,
The uneven shape includes at least one of a curved line and a polygonal line connecting a plurality of line segments at the boundary between the convex portion and the concave portion when viewed from the normal direction.
An optical element characterized by. In the optical element according to claim 1 or 2.
The concave-convex shape is a diffraction grating, and emits a pattern in which at least four primary diffracted lights and two or more axial directions are emitted.
An optical element characterized by. In the optical element according to claim 3,
The uneven shape is a diffraction grating, and the diffraction angle of at least four or more patterns of the primary diffracted light when light having a wavelength of 550 nm is input from the front is 8 degrees or more.
An optical element characterized by. In the optical element according to claim 3,
The uneven shape is a diffraction grating, and the diffraction angle of at least four or more patterns of the primary diffracted light when light having a wavelength of 550 nm is input from the front is 10 degrees or more.
An optical element characterized by. In the optical element according to any one of claims 3 to 5.
The uneven shape has a unit region which is a region of a diffraction grating capable of emitting the pattern, and a plurality of the unit regions are arranged in the mark.
An optical element characterized by. In the optical element according to any one of claims 1 to 6.
It has an optical functional area that exerts the optical function of the optical element.
The mark is arranged around the optical functional area,
An optical element characterized by. In the optical element according to claim 7,
The optical functional region includes a diffraction grating.
An optical element characterized by. In the optical element according to claim 8,
The uneven shape is a diffraction grating and has the same uneven height as the diffraction grating in the optical functional region.
An optical element characterized by. In the optical element according to claim 8 or 9.
The uneven shape is a diffraction grating, and is composed of a diffraction grating having the same design as the diffraction grating in the optical functional region.
An optical element characterized by.